When ordered to evacuate, what should the "B" flight attendant do first?

The appropriate first action for the "B" flight attendant when ordered to evacuate is to activate the emergency lights. This step is crucial because it ensures that passengers can see clearly during the evacuation, especially in low-light or chaotic conditions. The illumination provided by the emergency lights helps guide passengers to the exits safely and can prevent injuries during the evacuation process.

While other actions such as checking for smoke or opening the nearest exit may be critical in the overall evacuation procedure, they should take place after ensuring that the environment is sufficiently illuminated for a smooth evacuation. Proper visibility can be lifesaving, particularly in emergencies where time is of the essence, and confusion can lead to accidents.